The present invention relates to a prosthetic appliance, and particularly to a prosthetic appliance intended to replace an amputated extremity or limb of a human body.
There are already known various prosthetic appliances of the type here under consideration, which are used for replacement of severed human feet or hands. The present invention will be described as employed in a prosthetic appliance which takes the place of a severed foot; however, it is to be understood that a similar concept may also be used in a prosthetic appliance for replacing an amputated hand.
Usually, the conventional prosthetic appliances include a supporting part which is connected to the body of the user, a foot or other extremity part which is connected to the free end portion of the supporting part, and a sheath made of an elastically yieldable material, preferably foamed rubber or synthetic plastic material which surrounds at least the supporting part of the appliance and gives the same an aesthetically pleasing appearance. Inasmuch as the primary purpose for the sheath, besides protecting the supporting element from detrimental influences of the environment, is to improve the appearance of the prosthetic appliance, it will be hereafter called a cosmetic sheath.
In the conventional prosthetic appliances, the extremity-shaped part is made of a rigid material, such as wood, synthetic plastic material or the like, and the cosmetic sheath, as already mentioned above, is made of a resiliently yieldable material. In order to give the prosthetic appliance a compact outlook, it is necessary to connect the cosmetic sheath with the foot or other extremity part. This, however, brings about a variety of problems.
First of all, only certain types of connecting procedures which do not impair the appearance of the prosthetic appliance can be used for connecting the cosmetic sheath to the extremity-shaped part. Such procedures primarily involve gluing or welding, particularly thermal welding. These procedures, as is well known, result in permanent bonds which are not easy to dissociate without damaging or destroying one of the connected components.
Another problem results from the fact that some of the various components of the prosthetic appliance are connected with one another using adjustable connecting elements. The adjustment of the position of the various components relative to one another may itself result in impairment of the appearance of the resiliently yieldable cosmetic sheath. However, more importantly, after the original adjustment, any subsequent adjustment of the positions of the various components relative to one another requires that access be obtained to the components the positions of which are to be adjusted. Most of the time, such access may be had only upon removal or partial removal of the cosmetic sheath which, in the event of a permanent bond between the cosmetic sheath and the extremity-shaped part, necessitates at least a partial cutting up of the bond between the cosmetic sheath and the extremity-shaped part which is glued or welded thereto, or of the cosmetic sheath proper. When the former approach is taken, it may be very difficult to reestablish a permanent bond between the cosmetic sheath and the extremity-shaped part. In the latter event, the damaged cosmetic sheath must be restored to its original appearance, to the extent possible, by gluing or otherwise connecting the cut-up sections of the cosmetic sheath. This, of course, is very difficult to do, particularly when it is desired, as it always is, to restore the aesthetically pleasing intact appearance of the sheath.
In order to avoid this difficulty, it has been already proposed to connect the cosmetic sheath to the extremity-shaped part by inserting the end portion of the cosmetic sheath into a recess formed in the end face of the extremity-shaped part. However, experience with this approach has shown that such a connection is not particularly reliable, especially because of the fact that only frictional engagement of the end portion of the cosmetic sheath with the surfaces bounding the recess is obtained. Also, the outward appearance of the prosthetic device leaves much to be desired inasmuch as formation of visible seams is unavoidable when this approach is taken.
An attempt has already been made to avoid these drawbacks which are inherent to the solution in which the cosmetic sheath is directly connected to the extremity-shaped part of the prosthetic appliance either by an end-to-end gluing or welding, or by inserting the end portion of the cosmetic sheath into a recess of the extremity-shaped part. In this approach, which has been heretofore used only in prosthetic appliances in which there is no relative movement between the various components, a connecting element is interposed between the cosmetic sheath and the extremity-shaped part, such connecting element being of a plate-shaped configuration and being permanently connected to the cosmetic sheath. In this prior-art appliance, the connecting element has an exposed surface having at least two receiving recesses which extend normal to the exposed surface, opening thereon and leading into the plate-shaped connecting element, and the extremity-shaped part, such as a foot part, has an equal number of pins which are clampingly received within the corresponding recesses of the connecting element. In addition to the recesses, the plate-shaped connecting element is also provided with a central opening through which an end portion of a supporting element extends from the space surrounded by the cosmetic sheath toward the foot-shaped part.
In this prior-art appliance, the connection between the cosmetic sheath, and particularly between the plate-shaped connecting element which is permanently connected thereto, and the extremity-shaped part, can be established in a very simple manner in that the connecting element is aligned with the extremity-shaped part so that the pins of the extremity-shaped part are brought into registry with the recesses of the connecting element, whereupon the sheath or the connecting element is pressed against the extremity-shaped part to thereby obtain a clamping connection between the pins and the complementary recesses. Such connection can just as easily be discontinued by pulling the connecting element away from the extremity-shaped part. In view of the fact that the connecting element can be so shaped as to exactly correspond to the contour of the connecting surface of the extremity-shaped part of the prosthetic appliance, it is assured that, no matter now many times the connection between the cosmetic sheath and the extremity-shaped part is established and discontinued, the outer surfaces of the cosmetic sheath, the connecting element and the extremity-shaped part will always smoothly and gradually merge with one another without formation of any perceivable seams. It will be appreciated that, in this prior-art prosthetic appliance, the connection of the cosmetic sheath or of the connecting element permanently attached thereto with the extremity-shaped part of the prosthetic device can be arbitrarily often discontinued and reestablished without any damage to such connection or to the cosmetic sheath. In addition thereto, the fact that the connecting element is of a plate-shaped configuration and is permanently connected to the cosmetic sheath significantly contributes to reinforcing and stabilizing the cosmetic sheath and particularly the free end portion thereof, which is a very important consideration in view of the fact that the cosmetic sheath is usually made of a comparably weak or resiliently yieldable material, such as a foamed synthetic plastic material. Moreover, the pin-and-recess connection of the connecting elements with the extremity-shaped part assures that the cosmetic sheath reassumes its original position after each reassembly of the extremity-shaped part with the remainder of the prosthetic appliance.
It may be seen that the immediately above described prior-art prosthetic appliance has a number of advantages, particularly where the connection of the cosmetic sheath with the extremity-shaped part is concerned. However, as already previously mentioned, this approach does not readily lend itself for use in a prosthetic appliance in which the various components are articulated to one another, particularly in an appliance in which the extremity-shaped part is pivotally connected to the supporting part. Such articulated prosthetic appliances are also very well known and usually they include a tilting element which is pivotally supported on the extremity-shaped part and to which a tubular element of the supporting part, as well as the cosmetic sheath, are connected. This solution has a very important disadvantage in that, as the tilting element is angularly displaced relative to the extremity-shaped part, the cosmetic sheath which is connected to the tilting element is deformed, which results in an impairment of aesthetic appearance of the prosthetic appliance which, in most instances, is unacceptable to the user of the prosthetic appliance. Various solutions to this problem have already been attempted; however, such solutions are either very complex and thus impractical, or do not result in any significant improvement of the appearance of the prosthetic appliance during the use thereof.